Friday, 19 July 2013



Information is stored in databases.
Database – maintains information about various types of objects (inventory), events (transactions), people (employees), and places (warehouses)

Database models include:

  • Hierarchical database model – information is organized into a tree-like structure (using parent/child relationships) in such a way that it cannot have too many relationships
  • Network database model – a flexible way of representing objects and their relationships
  • Relational database model – stores information in the form of logically related two-dimensional tables

Entity – a person, place, thing, transaction, or event about which information is stored
The rows in each table contain the entities

Attributes (fields, columns) – characteristics or properties of an entity class
The columns in each table contain the attributes

Primary keys and foreign keys identify the various entity classes (tables) in the database:

  • Primary key – a field (or group of fields) that uniquely identifies a given entity in a table
  • Foreign key – a primary key of one table that appears an attribute in another table and acts to provide a logical relationship among the two tables

 Database advantages from a business perspective include:

  • Increased flexibility
  • Increased scalability and performance
  • Reduced information redundancy
  • Increased information integrity (quality)
  • Increased information security

A well-designed database should :
  • Handle changes quickly and easily
  • Provide users with different views
  • Have only one physical view
  • --Physical view – deals with the physical storage of information on a storage device

  • Have multiple logical views
  • --Logical view – focuses on how users logically access information

A database must scale to meet increased demand,  while maintaining acceptable performance levels

  • Scalability – refers to how well a system can adapt to increased demands
  • Performance – measures how quickly a system performs a certain process or transaction

Information integrity – measures the quality of information

Integrity constraint – rules that help ensure the quality of information

  • Relational integrity constraint
  • Business-critical integrity constraint

Databases offer several security features including:

  • Password – provides authentication of the user
  • Access level – determines who has access to the different types of information
  • Access control – determines types of user access, such as read-only access

Database management systems (DBMS) – software through which users and application programs interact with a database.

Data-driven Web sites – an interactive Web site kept constantly updated and relevant to the needs of its customers through the use of a database.

 Integration – allows separate systems to communicate directly with each other :

  • Forward integration – takes information entered into a given system and sends it automatically to all downstream systems and processes
  • Backward integration – takes information entered into a given system and sends it automatically to all upstream systems and processes

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